In medical procedures it is common for medical personnel to select a sample (e.g. biopsy) based on tissue appearance. For external tissue (e.g. skin) selection may be based upon growth rate, color or other gross anatomic features. For internal tissue (e.g. colon, bladder or stomach) an endoscopic video image may be used to select tissue for biopsy.
Unfortunately, normal tissue and adjacent diseased tissue may often appear similar. In some cases, the tissue of interest may actually be covered by normal mucosa and/or normal tissue. This can make it difficult for medical personnel to select an informative sample based on visual analysis. For this reason, several biopsy samples are typically taken for analysis.
EP patent publication 1 568 307, the disclosure of which is incorporated herein by reference, describes use of luma and/or color features, and linear bandpass spatial filtering, multiple thresholding and logic operations on the multiply thresholded image regions. Image processing described in this application is well suited to detecting small areas with known dimensions in medical images.
US patent publication 2006/0039622, the disclosure of which is incorporated herein by reference, describes image processing methods which rely upon determination of luminance. While the luminance formula includes R, G and B terms, its function is to transform color data into grayscale values. Medical images are not specifically described in the context of the methods.
US patent publication 2005/0171409, the disclosure of which is incorporated herein by reference, describes analysis of “Pixel values” as a means of identifying lung nodules. This application employs a linear discriminant analysis and/or Multi-MTANN. Described methods are suitable for use in analysis of grey values and are not applicable to RGB color data.
US patent publication 2005/0078857, the disclosure of which is incorporated herein by reference, describes an organ searching algorithm for use in medical images and an image coloring algorithm. This application is concerned with converting PGM (grey-map) images to color while identifying organs. Use of RGB data of individual pixels to identify organs is not described as this data is not available from a grey scale map.
U.S. Pat. No. 6,975,898, the disclosure of which is incorporated herein by reference, describes medical image processing for diagnostic purposes. This patent employs directed and scanned optical illumination provided by a scanning optical fiber or light waveguide that is driven by a piezoelectric or other electromechanical actuator included at a distal end of an integrated imaging and diagnostic/therapeutic instrument. This patent teaches that “ . . . the white light illumination for standard endoscopic imaging is typically provided through an optical fiber bundle that diffusely illuminates the tissue and is incapable of providing a directed optical energy at high intensity and resolution to produce effective optical therapies, and will often not have the characteristics required for diagnostic processes.”.
U.S. Pat. No. 6,208,749, the disclosure of which is incorporated herein by reference, describes a method for computer controlled image analysis of digital skin tissue at a plurality of wavelengths, optionally including those outside of the red-green-blue bands. The described methods and systems can include the automatic characterization of the condition of the skin tissue, based on automatically computed values of parameters which are functions of characteristics of the skin tissue, based on the digital images. Absorbance/reflectance measurements for three spectral bands is apparently suggested as a suitable method for a medical diagnosis. Melanoma diagnosis is specifically considered.
U.S. Pat. No. 6,631,204, the disclosure of which is incorporated herein by reference, describes a similarity measurement method for the classification of medical images into predetermined categories. The described methods employ a small set of pre-classified images and employ a weighted linear combination of eigenvectors for each category. The eigenvectors are equivalent to the Red, Green and Blue base vectors used to describe the entire color space. A test image is provided and projected onto the eigenvectors of each of the categories so as to reconstruct the test image with the eigenvectors. The RMS (root-mean-square) distance between the eigenvectors of the test image and each of the categories is measured. The smallest similarity measurement distance is selected, and the test image is classified in accordance with the selected smallest similarity measurement distance.
U.S. Pat. No. 6,792,137, the disclosure of which is incorporated herein by reference, describes a method for providing a preliminary diagnosis of skin cancer, more specifically a screening risk assessment of pigmented moles and lesions by receiving digital photographs of skin abnormalities from a plurality of consumers at a server, receiving medical information related to each of the plurality of consumers at the server, assigning an identification to at least one of the consumers and the digital photographs, reviewing the digital photographs and categorizing the digital photographs into categories. Use of clinical photographs and/or epiluminescence microscopy (ELM) is described. Color information, if employed, is input manually in text fields.
EP patent 0 588 943, the disclosure of which is incorporated herein by reference, describes use of spatial smoothing operators to smooth images including medical images.
A commercially available HDTV-Compatible Endoscope (EVIS LUCERA; Olympus Industrial; KeyMed (Medical & Industrial Equipment) Ltd, Essex; UK) provides Diagnosis via Mucosal Hemoglobin Value-Responsive Chromatic Enhancement Function, and CV-180 HDTV and NBI processing unit.
U.S. Pat. No. 7,042,488, the disclosure of which is incorporated herein by reference, describes use of color filters for blood vessel color highlighting, including, (R-Y)/(B-Y), where Y is Luma.
U.S. Pat. No. 5,031,036, the disclosure of which is incorporated herein by reference, describes enhancement of endoscopic images acquired with white light, using a color filter, including (G-R).
U.S. Pat. No. 5,956,416, the disclosure of which is incorporated herein by reference, describes the use of three narrow spectral bands to enhance an image based upon an estimate of hemoglobin concentration. When a hemoglobin index IHb which is an indicator of the concentration of hemoglobin in mucosal tissue is calculated as IHb=32·Log2(R/B). The IHb color enhancement function works by calculating the average hemoglobin concentration of the tissue, and then displaying those areas with higher-than-average IHb values using more red, and areas with lower-than-average IHb values with more white. Additionally color enhancement is described.